Light-emitting device, illumination apparatus, and display apparatus

ABSTRACT

A light-emitting device includes: an organic layer which is interposed between a first electrode and a second electrode and in which a first light-emitting layer and a second light-emitting layer emitting light of single colors or two or more different colors in a visible wavelength region are sequentially included at mutually separated positions in that order in a direction from the first electrode to the second electrode; a first reflective interface which is provided on the side of the first electrode so as to reflect light emitted from the first light-emitting layer and the second light-emitting layer to be emitted from the side of the second electrode; and a second reflective interface and a third reflective interface which are sequentially provided on the side of the second electrode at mutually separated positions in that order in a direction from the first electrode to the second electrode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a light-emitting device, an illuminationapparatus, and a display apparatus. More specifically, the inventionrelates to a light-emitting device which uses electroluminescence of anorganic material, and an illumination apparatus and a display apparatususing the light-emitting device.

2. Description of the Related Art

Light-emitting devices (hereinafter referred to as organic EL devices)which use electroluminescence of an organic material have attractedattention as a light-emitting device capable of emitting high-luminancelight with low-voltage direct-current driving and have been activelyresearched and developed. The organic EL device has a structure in whichan organic layer having a light-emitting layer that generally has athickness of about several tens to several hundreds of nm is interposedbetween a reflective electrode and a translucent electrode. In such anorganic EL device, light emitted from the light-emitting layer isextracted to the outside after undergoing interference in the devicestructure. In the related art, several attempts have been made toimprove emission efficiency of the organic EL device using suchinterference.

JP-A-2002-289358 discloses a technique in which a distance from anemission position to a reflective layer is set so as to allow lighthaving an emission wavelength to resonate using interference of lightemitted from a light-emitting layer towards a translucent electrode andlight emitted towards a reflective electrode, thus enhancing emissionefficiency.

JP-A-2000-243573 defines a distance from an emission position to areflective electrode and the distance from the emission position to aninterface between a translucent electrode and a substrate by takingreflection of light at the interface between the translucent electrodeand the substrate into consideration.

WO01/039554 discloses a technique in which the thickness of a layerbetween a translucent electrode and a reflective electrode is set so asto allow light having a desired wavelength to resonate usinginterference of light occurring when light undergoes multiplereflections between the translucent electrode and the reflectiveelectrode, thus enhancing emission efficiency.

Japanese Patent No. 3508741 discloses a method of controlling anattenuation balance of the three colors red (R), green (G), and blue (B)by controlling the thickness of an organic layer as a method ofimproving the viewing angle characteristics of a white chromaticitypoint in a display apparatus having a light-emitting device in whichemission efficiency is enhanced using a cavity structure.

The techniques mentioned above are directed to an organic EL devicewhich uses interference of emitted light in order to enhance emissionefficiency. In such an organic EL device, when the bandwidth of aninterference filter for extracted light h narrows, the wavelength of thelight h shifts largely when the emission surface is viewed from anoblique direction, and the emission intensity decreases. Thus, theviewing-angle dependency of emission characteristics increases.

In contrast, JP-A-2006-244713 discloses a technique in which the phaseof light emission by a reflective layer of an organic EL device having anarrow single-color spectrum and the interference by a single reflectivelayer provided on the light emitting side are set to be in an oppositephase to the central wavelength, thus suppressing a variation of hue inaccordance with a viewing angle.

In an organic light-emitting device having white light-emitting layersstacked sequentially, since the interference as above occurs in thedevice, in order to effectively extract white emission having a widewavelength component, it is preferable for the emission position to bepositioned close to the reflective layer particularly at a distance of80 nm or less. When the emission position is separated from thereflective layer and the distance increases, it is difficult to obtainwhite emission having a wide spectrum due to the interference.

JP-A-2004-79421 discloses a technique in which a distance from theemission position to a reflective layer and a distance from the emissionposition to the interface between a translucent electrode and an outerlayer are defined so as to obtain a high-efficiency light-emittingdevice having excellent white chromaticity.

JP-A-2006-244712 discloses a technique which enables a good whitechromaticity point to be obtained by adopting the interference of theopposite phase as disclosed in JP-A-2006-244713. However, since it isdifficult to achieve phase cancellation over a wide wavelength range,similarly to JP-A-2006-244713, there is no discussion regardingsuppression of a variation in hue in accordance with the viewing angleas compared to a single color.

JP-A-2006-173550, JP-T-2008-511100, and JP-T-2008-518400, for example,disclose a technique in which a plurality of light-emitting layers isstacked with an intermediate layer disposed therebetween in order toenhance emission efficiency and improve the light emission lifecycle,thus forming an organic layer so as to have a stacked structure (aso-called tandem structure) having light-emitting layers connected inseries. In this type of organic layer, an arbitrary number oflight-emitting layers can be stacked. In this case, particularly, bystacking a blue light-emitting layer generating blue light, a greenlight-emitting layer generating green light, and a red light-emittinglayer generating red light, it is possible to generate white light as acombined light of the blue, green, and red light.

However, when the tandem structure as above is formed, it is difficultto make all the distances from the respective emission positions to thereflective layer to be 80 nm or less. Moreover, since the viewing-angledependency of luminance and hue is very high, the intensity distributionproperties of an illumination apparatus or the display properties of adisplay apparatus are greatly decreased.

SUMMARY OF THE INVENTION

It is therefore desirable to provide a light-emitting device capable ofeffectively extracting light in a wide wavelength range and greatlyreducing a viewing-angle dependency of luminance and hue with respect tolight of a single color or a combined color of plural colors.

It is also desirable to provide an illumination apparatus which has asmall viewing-angle dependency and good intensity distributionproperties.

It is also desirable to provide a display apparatus which has a highdisplay quality and a small viewing-angle dependency.

According to an embodiment of the present invention, there is provided alight-emitting device including:

an organic layer which is interposed between a first electrode and asecond electrode and in which a first light-emitting layer and a secondlight-emitting layer emitting light of single colors or two or moredifferent colors in a visible wavelength region are sequentiallyincluded at mutually separated positions in that order in a directionfrom the first electrode to the second electrode;

a first reflective interface which is provided on the side of the firstelectrode so as to reflect light emitted from the first light-emittinglayer and the second light-emitting layer to be emitted from the side ofthe second electrode; and

a second reflective interface and a third reflective interface which aresequentially provided on the side of the second electrode at mutuallyseparated positions in that order in a direction from the firstelectrode to the second electrode,

wherein when an optical distance between the first reflective interfaceand a luminescent center of the first light-emitting layer is L11, anoptical distance between the first reflective interface and aluminescent center of the second light-emitting layer is L21, an opticaldistance between the luminescent center of the first light-emittinglayer and the second reflective interface is L12, an optical distancebetween the luminescent center of the second light-emitting layer andthe second reflective interface is L22, an optical distance between theluminescent center of the first light-emitting layer and the thirdreflective interface is L13 , an optical distance between theluminescent center of the second light-emitting layer and the thirdreflective interface is L23, a central wavelength of an emissionspectrum of the first light-emitting layer is Xl, and a centralwavelength of an emission spectrum of the second light-emitting layer isλ2, L11, L21, L12, L22, L13, and L23 are chosen so as to satisfy all theexpressions (1) to (6) and at least one of the expressions (7) and (8).

2L11/λ11+φ1/2π=0  (1)

2L21/λ21+φ1/2π=n (where n≧1)  (2)

λ1−150<λ11<λ1+80  (3)

λ2−30<λ21<λ2+80  (4)

2L12/λ12+φ2/2π=m′+1/2 and 2L13/λ13+φ3/2π=m″, or 2L12/λ12+φ2/2π=m′ and 2L13/λ13+φ3/2π=m″+1/2  (5)

2L22/λ22+φ2/2π=n′+1/2 and 2L 23/λ23+φ3/2π=n″, or 2L22/λ22+φ2/2π=n′ and2L23/λ23+φ3/2π=n″+1/2, or 2L22/λ22+φ2/2π=n′+1/2 and2L23/λ23+φ3/2π=n″+1/2  (6)

λ22<λ2−15 or λ23>λ2+15  (7)

λ23<λ2−15 or λ22>λ2+15  (8)

where m′, m″, n, n′, n″ are integers,

λ1, λ2, λ11, λ21, λ12, λ22, λ13, and λ23 are in units of nm,

φ1 is a phase shift occurring when light of each wavelength is reflectedby the first reflective interface,

φ2 is a phase shift occurring when light of each wavelength is reflectedby the second reflective interface, and

φ3 is a phase shift occurring when light of each wavelength is reflectedby the third reflective interface.

According to another embodiment of the present invention, there isprovided an illumination apparatus including:

at least one light-emitting device,

wherein the light-emitting device includes

an organic layer which is interposed between a first electrode and asecond electrode and in which a first light-emitting layer and a secondlight-emitting layer emitting light of single colors or two or moredifferent colors in a visible wavelength region are sequentiallyincluded at mutually separated positions in that order in a directionfrom the first electrode to the second electrode;

a first reflective interface which is provided on the side of the firstelectrode so as to reflect light emitted from the first light-emittinglayer and the second light-emitting layer to be emitted from the side ofthe second electrode; and

a second reflective interface and a third reflective interface which aresequentially provided on the side of the second electrode at mutuallyseparated positions in that order in a direction from the firstelectrode to the second electrode,

wherein when an optical distance between the first reflective interfaceand a luminescent center of the first light-emitting layer is L11, anoptical distance between the first reflective interface and aluminescent center of the second light-emitting layer is L21, an opticaldistance between the luminescent center of the first light-emittinglayer and the second reflective interface is L12, an optical distancebetween the luminescent center of the second light-emitting layer andthe second reflective interface is L22, an optical distance between theluminescent center of the first light-emitting layer and the thirdreflective interface is L13, an optical distance between the luminescentcenter of the second light-emitting layer and the third reflectiveinterface is L23, a central wavelength of an emission spectrum of thefirst light-emitting layer is Xl, and a central wavelength of anemission spectrum of the second light-emitting layer is X2, L11, L21,L12, L22, L13, and L23 are chosen so as to satisfy all the expressions(1) to (6) and at least one of the expressions (7) and (8).

According to still another embodiment of the present invention, there isprovided a display apparatus including:

at least one light-emitting device,

wherein the light-emitting device includes

an organic layer which is interposed between a first electrode and asecond electrode and in which a first light-emitting layer and a secondlight-emitting layer emitting light of single colors or two or moredifferent colors in a visible wavelength region are sequentiallyincluded at mutually separated positions in that order in a directionfrom the first electrode to the second electrode;

a first reflective interface which is provided on the side of the firstelectrode so as to reflect light emitted from the first light-emittinglayer and the second light-emitting layer to be emitted from the side ofthe second electrode; and

a second reflective interface and a third reflective interface which aresequentially provided on the side of the second electrode at mutuallyseparated positions in that order in a direction from the firstelectrode to the second electrode,

wherein when an optical distance between the first reflective interfaceand a luminescent center of the first light-emitting layer is L11, anoptical distance between the first reflective interface and aluminescent center of the second light-emitting layer is L21, an opticaldistance between the luminescent center of the first light-emittinglayer and the second reflective interface is L12, an optical distancebetween the luminescent center of the second light-emitting layer andthe second reflective interface is L22, an optical distance between theluminescent center of the first light-emitting layer and the thirdreflective interface is L13, an optical distance between the luminescentcenter of the second light-emitting layer and the third reflectiveinterface is L23, a central wavelength of an emission spectrum of thefirst light-emitting layer is λ1, and a central wavelength of anemission spectrum of the second light-emitting layer is λ2, L11, L21,L12, L22, L13, and L23 are chosen so as to satisfy all the expressions(1) to (6) and at least one of the expressions (7) and (8).

The luminescent centers of the first light-emitting layer and the secondlight-emitting layer mean a plane where the peaks of the emissionintensity distribution in the thickness direction thereof arepositioned. In a light-emitting layer emitting light of a single color,the luminescent center is generally a plane that evenly divides thethickness thereof. In a light-emitting layer emitting light of two ormore different colors, when the luminescent centers can be regarded asidentical since the thickness of the layer emitting light of each colorare sufficiently small, the luminescent center is generally the planethat evenly divides the thickness thereof.

The expression (1) is an expression for setting the optical distancebetween the first reflective interface and the luminescent center of thefirst light-emitting layer so that light having the central wavelengthof the emission spectrum of the first light-emitting layer is reinforcedthrough interference between the first reflective interface and theluminescent center of the first light-emitting layer. The expression (2)is an expression for setting the optical distance between the firstreflective interface and the luminescent center of the secondlight-emitting layer so that light having the central wavelength of theemission spectrum of the second light-emitting layer is reinforcedthrough interference between the first reflective interface and theluminescent center of the second light-emitting layer. The expressions(5) and (6) are expressions for setting the constructive and destructiveconditions for at least one of the reflection of light by the secondreflective interface and the reflection of light by the third reflectiveinterface while the interference wavelengths are shifted from thecentral wavelength of the emission spectrum of the first light-emittinglayer and the central wavelength of the emission spectrum of the secondlight-emitting layer (λ12≠λ13 or λ22≠λ23). The expressions (7) and (8)are conditions for broadening the interference wavelengths. The valuesof λ11, λ21, λ12, λ22, λ13, λ23 in the expressions (1), (2), (5), and(6) are calculated from the values of λ1 and λ2 by the expressions (3),(4), (7), and (8).

The integers m′, m″, n, n′, and n″ are chosen as necessary. In order toincrease the amount of light extracted from the light-emitting device,the integer n is preferably set as n≦5, and most preferably as n=1 orn=2.

According to this light-emitting device, the peaks of the spectraltransmittance curve of an interference filter can be made substantiallyflat in the visible wavelength region, or the slopes thereof can be madesubstantially the same in the wavelength range of all emission colors.Therefore, a decrease of luminance at a viewing angle of 45° can becontrolled to be 30% or less with respect to luminance at a viewingangle of 0°, and a chromaticity shift of Δuv≦0.015 can be obtained.

This light-emitting device may be a top emission-type light-emittingdevice and may be a bottom emission-type light-emitting device. In a topemission-type light-emitting device, the first electrode, the organiclayer, and the second electrode are sequentially stacked on a substrate.In a bottom emission-type light-emitting device, the second electrode,the organic layer, and the first electrode are sequentially stacked on asubstrate. The substrate of the top emission-type light-emitting devicemay be opaque or transparent, which is chosen as necessary. Thesubstrate of the bottom emission-type light-emitting device istransparent in order to extract light emitted from the side of thesecond electrode to the outside.

A metal layer having a thickness allowing transmission of visible lightmay be provided between the second light-emitting layer and the secondelectrode as necessary. The thickness of the metal layer may be 5 nm orless, and preferably 3 to 4 nm or less. The metal layer can be used as asemitransparent reflective layer.

One or plural reflective interfaces may be provided in addition to thefirst, second, and third reflective interfaces, as necessary. Moreover,at least one of the first, second, and third reflective interfaces maybedivided into a plurality of reflective interfaces, as necessary. Bydoing so, it is possible to broaden a wavelength range in which thereflection of light by the second reflective interface and thereflection of light by the third reflective interface are weakened andwidening the flat portions of the peaks of the spectral transmittancecurve of the interference filter for each emission region, thusimproving the viewing angle characteristics.

When the luminescent centers of light-emitting layers of the first orsecond light-emitting layer emitting light of two or more differentcolors may not be regarded as identical, the light-emitting devicepreferably further includes a reflective layer which is provided so asto maintain the flatness of the peaks of a spectral transmittance curveof an interference filter of the light-emitting device. The reason whythe luminescent centers of the light-emitting layers emitting light oftwo or more different colors may not be regarded as identical may bebased on the fact that the thickness of the layers emitting light ofeach color is thick or may be based on the stacking order of theselayers.

In this light-emitting device, there is a case where an additionalreflective layer is formed so as to improve reliability or comply withan employed configuration, and thus an additional reflective interfaceis formed. In that case, by forming a third reflective interfacenecessary for an optical operation and then forming a layer having athickness of at least 1 μm or more, it is possible to substantiallyignore the effect of subsequent interference. At that time, an arbitrarymaterial can be used as a material of the outer side of the thirdreflective interface and the material can be appropriately chosen inaccordance with the type of the light-emitting device. Specifically, atleast one or two or more of a transparent electrode layer having athickness of 1 μm or more, a transparent insulating layer, a resinlayer, a glass layer, and an air layer is formed on the outer side ofthe third reflective interface. However, the present invention is notlimited to this.

The illumination apparatus and the display apparatus according to theembodiments of the present invention may have the known configurationand can be appropriately configured in accordance with the purposes orfunctions thereof. As a typical example, the display apparatus includesa driving substrate on which an active device (for example, a thin-filmtransistor) is provided so as to supply a display signal correspondingto every display pixel to the light-emitting device, and a sealingsubstrate provided so as to face the driving substrate. Thelight-emitting device is disposed between the driving substrate and thesealing substrate. The display apparatus may be a white displayapparatus, a black-and-white display apparatus, or a color displayapparatus. In a color display apparatus, a color filter which transmitslight emitted from the side of the second electrode is typicallyprovided on a substrate that is disposed on the side of the secondelectrode of the light-emitting device among the driving substrate andthe sealing substrate.

According to the embodiments of the present invention, it is possible torealize providing a light-emitting device capable of effectivelyextracting light in a wide wavelength range and greatly reducing aviewing-angle dependency of luminance and hue with respect to light of asingle color or a combined color of two or more different colors in thevisible wavelength region.

According to the embodiments of the present invention, by using thelight-emitting device, it is possible to realize an illuminationapparatus which has a small viewing-angle dependency and good intensitydistribution properties and a display apparatus which has a high displayquality and a small viewing-angle dependency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional diagram showing an organic EL device according toa first embodiment of the present invention.

FIG. 2 is a schematic diagram showing the spectral transmittance curvesof an interference filter formed by a first reflective interface in theorganic EL device according to the first embodiment of the presentinvention.

FIG. 3 is a schematic diagram showing spectral transmittance curves ofan interference filter formed by a first reflective interface and acombined interference filter formed by first and second reflectiveinterfaces in the organic EL device according to the first embodiment ofthe present invention.

FIG. 4 is a schematic diagram showing the spectral transmittance curvesof a combined interference filter formed by first, second, and thirdreflective interfaces in the organic EL device according to the firstembodiment of the present invention.

FIG. 5 is a schematic diagram showing the luminance-viewing anglecharacteristics of the organic EL device according to the firstembodiment of the present invention.

FIG. 6 is a schematic diagram showing the chromaticity-viewing anglecharacteristics of the organic EL device according to the firstembodiment of the present invention.

FIGS. 7A and 7B are sectional diagrams showing a case where a secondlight-emitting layer of the organic EL device according to the firstembodiment of the present invention is thick so that the luminescentcenters may not be regarded as identical.

FIG. 8 is a schematic diagram showing the spectral transmittance curvesof an interference filter corresponding to the second light-emittinglayer of the organic EL device according to the first embodiment of thepresent invention shown in FIGS. 7A and 7B.

FIG. 9 is a sectional diagram showing an organic EL device according toa third embodiment of the present invention.

FIG. 10 is a schematic diagram showing the spectral transmittance curvesof an interference filter corresponding to a second light-emitting layerof the organic EL device according to the third embodiment of thepresent invention.

FIG. 11 is a schematic diagram showing the luminance-viewing anglecharacteristics of the organic EL device according to the thirdembodiment of the present invention.

FIG. 12 is a schematic diagram showing the chromaticity-viewing anglecharacteristics of the organic EL device according to the thirdembodiment of the present invention.

FIG. 13 is a sectional diagram showing a top emission-type organic ELdevice according to Example 1.

FIG. 14 is a sectional diagram showing a bottom emission-type organic ELdevice according to Example 2.

FIG. 15 is a sectional diagram showing an organic EL illuminationapparatus according to a fourth embodiment of the present invention.

FIG. 16 is a sectional diagram showing an organic EL display apparatusaccording to a fifth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, modes (hereinafter referred to as embodiments) for carryingout the present invention will be described. The description will begiven in the following order:

1. First Embodiment (Organic EL Device);

2. Second Embodiment (Organic EL Device);

3. Third Embodiment (Organic EL Device);

4. Fourth Embodiment (Organic EL Illumination apparatus); and

5. Fifth Embodiment (organic EL display apparatus)

1. First Embodiment Organic EL Device

FIG. 1 shows an organic EL device according to a first embodiment.

As shown in FIG. 1, in this organic EL device, an organic layer 13 isinterposed between a first electrode 11 and a second electrode 12, inwhich a first light-emitting layer 13 a and a second light-emittinglayer 13 b are sequentially included in the organic layer 13 at mutuallyseparated positions in that order in the direction from the firstelectrode 11 to the second electrode 12. Like the existing organic ELdevice, a hole injection layer, a hole transport layer, an electrontransport layer, an electron injection layer, and the like, asnecessary, are formed in portions of the organic layer 13 above or underthe first light-emitting layer 13 a and above or under the secondlight-emitting layer 13 b. In this case, the second electrode 12 is atransparent electrode that transmits visible light, and light is emittedfrom the side of the second electrode 12. The first light-emitting layer13 a and the second light-emitting layer 13 b emit light of singlecolors or two or more different colors in the visible wavelength region.The emission wavelengths of the first light-emitting layer 13 a and thesecond light-emitting layer 13 b are appropriately chosen in accordancewith the color of light that is to be emitted from the organic ELdevice. In this embodiment, the first light-emitting layer 13 a emitslight of two different colors in the visible wavelength region, and thesecond light-emitting layer 13 b emits light of a single color. In thiscase, the first light-emitting layer 13 a is formed by twolight-emitting layers a1 and a2 that emit light of different colors. Forexample, when this organic EL device is used as a white light-emittingdevice, the first light-emitting layer 13 a emits light of green andred. In this case, the light-emitting layer a1 emits green light, andthe light-emitting layer a2 emits red light. Moreover, the secondlight-emitting layer 13 b emits blue light. The thicknesses of thelight-emitting layers a1 and a2 are chosen to be sufficiently small sothat the luminescent centers of the light-emitting layers a1 and a2 canbe regarded as identical. A conductive transparent layer 14 is formedbetween the organic layer 13 and the second electrode 12. Thetransparent layer 14 may be formed by two or more layers, as necessary.The first and second electrodes and 12, the organic layer 13, the firstand second light-emitting layers 13 a and 13 b, and the transparentlayer 14 can be formed by known materials, and the materials thereof areappropriately chosen as necessary.

The refractive index of the organic layer 13 is different from therefractive index of the first electrode 11, and a first reflectiveinterface 15 is formed between the first electrode 11 and the organiclayer 13 due to the difference in the refractive index. The firstreflective interface 15 may be formed at a position separated from thefirst electrode 11, as necessary. The first reflective interface 15 hasa function of reflecting light emitted from the first light-emittinglayer 13 a and the second light-emitting layer 13 b to be emitted fromthe side of the second electrode 12. The refractive index of thetransparent layer 14 is different from the refractive index of theorganic layer 13, and a second reflective interface 16 is formed betweenthe organic layer 13 and the transparent layer 14 due to the differencein the refractive index. Moreover, the refractive index of thetransparent layer 14 is different from the refractive index of thesecond electrode 12, and a third reflective interface 17 is formedbetween the transparent layer 14 and the second electrode 12 due to thedifference in the refractive index.

In FIGS. 1, L11, L21, L12, L22, L13, and L23 are illustrated atcorresponding positions. In the organic EL device, L11, L21, L12, L22,L13, and L23 are set so that all the expressions (1) to (6) aresatisfied and at least one of the expressions (7) and (8) is satisfied.

A case where the organic EL device is a white light-emitting device willbe described in detail.

In the white organic EL device, the first light-emitting layer 13 aemits light of green and red, the second light-emitting layer 13 b emitsblue light, and white light is extracted as a combined color of thesecolors. The central wavelength λ1 of the emission spectrum of the firstlight-emitting layer 13 a is 575 nm, for example, and the centralwavelength λ2 of the emission spectrum of the second light-emittinglayer 13 b is 460 nm, for example.

L11 is set so that light having the central wavelength λ1 of theemission spectrum of the first light-emitting layer 13 a is reinforcedthrough interference between the first reflective interface 15 and theluminescent center of the first light-emitting layer 13 a. Moreover, L21is set so that light having the central wavelength λ2 of the emissionspectrum of the second light-emitting layer 13 b is reinforced throughinterference between the first reflective interface 15 and theluminescent center of the second light-emitting layer 13 b. This statecan be expressed as the following expressions, and the expressions (1)to (4) are satisfied. In this case, since the first light-emitting layer13 a is at a position where 0-order (see the expression (1))interference occurs, a high transmittance is obtained over a widewavelength range (see the transmittance of an interference filter of thefirst reflective interface 15 for the first light-emitting layer 13 ashown in FIG. 2). Moreover, the interference wavelength can be shiftedgreatly from the central wavelength λ1 of the emission spectrum as shownin the expression (3).

2L11/λ11+φ1/2π=0  (1)′

2L21/λ21+φ1/2π=1  (2)′

where,

λ1−150=425<λ11=540<λ1+80=655 nm  (3)′

λ2−30=430<λ21=480<λ2+80=460+80=540 nm  (4)′

In the expressions, φ1 can be calculated from n and k of a complexrefractive index N=n−jk (n: refractive index, k: absorption coefficient)of the first electrode 11 and the refractive index n₀ of the organiclayer 13 in contact with the first electrode 11 (see, for example,Principles of Optics, Max Born and Emil Wolf, 1974 (PERGAMON PRESS)).The refractive indices of the organic layer 13, the transparent layer14, and the like can be measured using a spectroscopic ellipsometer.

A specific calculation example of φ1 will be described. When the firstelectrode 11 is made from an aluminum (Al) alloy, n=0.908 and k=5.927for light having a wavelength of 575 nm (corresponding to the centralwavelength λ1 of the emission spectrum of the first light-emitting layer13 a). When the refractive index n₀ of the organic layer 13 is set asn₀=1.75, the following expression is obtained.

φ1=tan⁻¹{2n ₀ k/(n ² +k ² −n ₀ ²)}=tan⁻¹(0.577)

Since −2π<φ1≦0, φ1 can be calculated as φ1=−2.618 radians. When thevalue of φ1 is substituted into the expression (1)′, L11 is calculatedas L11=114 nm. Moreover, when the value of φ1 is substituted into theexpression (2)′, L21 is calculated as L21=340 nm.

When the refractive index n of the first electrode 11 is larger than therefractive index n₀ of the organic layer 13, φ1 is shifted further by anamount of π radians. When the refractive index n is smaller than therefractive index n₀, the shift amount is 0.

Since the interference filter is in the constructive condition withrespect to the first and second light-emitting layers 13 a and 13 b, thespectral transmittance curves have peaks as shown in FIG. 2, and lightextraction efficiency is improved. However, when observed from theoblique direction, the wavelength range of the interference filter isshifted towards the short wavelengths, and luminance and hue arechanged. In addition, since the wavelength range of the interferencefilter corresponding to the second light-emitting layer 13 b is shiftedtowards the long wavelengths, white light is not sufficiently extracted.

Subsequently, the second reflective interface 16 is formed between theorganic layer 13 having the refractive index n₀=1.75 and the transparentlayer 14 having a refractive index (for example, 2.0) different from theorganic layer 13, and the third reflective interface 16 is formedbetween the transparent layer 14 and the second electrode 12 having arefractive index (for example, 1.8) different from the transparent layer14. Indium tin oxide (ITO) can be used as a material of the transparentlayer 14 having the refractive index of 2.0, and ITO or the like havinga different oxide composition can be used as a material of the secondelectrode 12 having the refractive index of 1.8. In this case, at leastone of the reflection of light by the second reflective interface 16 andthe reflection of light by the third reflective interface 17 satisfiesthe following conditions, that is, the constructive and destructiveconditions and a condition for broadening the interference wavelengthwhile the interference wavelengths are shifted from the centralwavelengths λ1 and λ2 (λ12≠λ13 or λ22≠λ23).

2L12/λ12+φ2/2π=1+1/2  (5)′

2L22/λ22+φ2/2π=1  (6)′

2L13/λ13+φ3/2π=3  (5)′

2L23/λ23+φ3/2π=2+1  (6)′

λ22=380 nm<λ2−15=445 nm  (7)′

(where λ12, λ22, λ13, and λ23 are in units of nm)

The values of φ2 and φ3 can be calculated by the same manner as above.

In this way, all the conditions of the expressions (1) to (7) aresatisfied.

FIG. 3 shows the spectral transmittance curves of the interferencefilter formed by the first and second reflective interfaces 15 and 16.In this case, since the wavelength conditions of the first and secondreflective interfaces 15 and 16 are different by an amount of 15 nm ormore, the transmittance decreases in a wavelength near 550 nm. Thus, thelight of the three colors R, G, and B may not be extracted in a wellbalanced manner, and white light may not be obtained. In addition, sincea flat portion may not be obtained in the spectral transmittance curve,the viewing angle characteristics exhibit a great change from luminanceand hue.

FIG. 4 shows the spectral transmittance curves of an interference filterwhich is formed by the first and second reflective interfaces 15 and 16,and in which the effect of the third reflective interface 17 isincluded. It can be understood from FIG. 4 that an interference filterof which the spectral transmittance curve is substantially flat in theblue region and the green and red regions is formed. The luminance andchromaticity-viewing angle characteristics in that state are shown inFIGS. 5 and 6, respectively. As is clear from FIGS. 5 and 6, theluminance at the viewing angle of 45° maintains 85% or more of theluminance at the viewing angle of 0°, and a chromaticity shift ofΔuv≦0.015 is also achieved.

As described above, according to the first embodiment, the organic ELdevice includes the organic layer 13 which is interposed between thefirst electrode 11 and the second electrode 12 and which includes thefirst and second light-emitting layers 13 a and 13 b emitting light ofsingle colors or light of two or more different colors in the visiblewavelength region. Moreover, the first reflective interface 15 is formedclose to the side of the first electrode 11, and the second reflectiveinterface 16 and the third reflective interface 17 are formed close tothe side of the second electrode 12 from which light is emitted.Moreover, the distances L11, L21, L12, L22, L13, and L23 shown in FIG. 1are set so that all the expressions (1) to (6) are satisfied and atleast one of the expressions (7) and (8) is satisfied. As a result, thisorganic EL device has an interference filter of which the transmittanceis high over a wide wavelength range and thus can effectively extractlight in a wide wavelength range. Therefore, according to this organicEL device, a white light-emitting device having good hue can berealized. Moreover, this organic EL device can achieve a remarkablereduction in the viewing-angle dependency of luminance and hue for asingle color or a combined color of two or more different colors.Furthermore, this organic EL device can allow choice of an emissioncolor by designing the first and second light-emitting layers 13 a and13 b. In addition, this organic EL device consumes less power since thetransmittance of the interference filter is high.

2. Second Embodiment Organic EL Device

In an organic EL device according to a second embodiment, the second andthird reflective interfaces 16 and 17 of the organic EL device accordingto the first embodiment are respectively divided into two front and rearreflective interfaces so as to broaden the wavelength range of theopposite-phase interference conditions shown in the expressions (5) and(6). That is, as for the expression (5), for example, when the secondreflective interface 16 is divided into two front and rear reflectiveinterfaces separated by a distance of Δ, L12 becomes L12+Δ and L12−Δ,the wavelength range of λ12 in which the expression (5) is satisfied isbroadened. The same applies to the expression (6).

According to the second embodiment, in addition to the same advantagesas the first embodiment, since the wavelength range of theopposite-phase interference condition shown in the expressions (5) and(6) can be broadened, it is possible to obtain an advantage that theviewing angle characteristics of the organic EL device can be improvedfurther.

3. Third Embodiment Organic EL Device

In the organic EL device according to the first embodiment, there is acase where the portions of the light-emitting layers a1 and a2 of thefirst light-emitting layer 13 a are formed by a stacked structure madeup of a plurality of layers depending on a manufacturing method of theorganic EL device or in order to obtain necessary properties. Thus, theportions become thick. Moreover, as for the stacking order of the greenlight-emitting layer a1 and the red light-emitting layer a2, it ispreferable to stack the layers in the descending order of the emissionwavelength from the side of the first electrode 11. That is, the greenlight-emitting layer a1 and the red light-emitting layer a2 arepreferably stacked in that order from the side of the first electrode 11similarly to the first embodiment. However, the stacking order of thegreen light-emitting layer a1 and the red light-emitting layer a2 may bereversed. In such a case, since it is difficult to regard theluminescent center of the light-emitting layer a1 to be identical to theluminescent center of the light-emitting layer a2, it is difficult tomaintain wide-viewing angle characteristics. As for a countermeasure,the viewing angle characteristics can be improved by additionallyproviding a fourth reflective interface in addition to the first,second, and third reflective interfaces 15, 16, and 17 of the organic ELdevice according to the first embodiment.

In the fourth reflective interface, depending on the staking order ofthe light-emitting layer a1 and the light-emitting layer a2, both theconstructive and destructive conditions exist in the range of thecentral wavelength±15 nm of these light-emitting layers a1 and a2. FIG.7A shows the organic EL device according to the first embodiment. Inthis case, the thicknesses of the green light-emitting layer a1 and thered light-emitting layer a2 are sufficiently small, and the luminescentcenter of the light-emitting layer a1 can be regarded as identical tothe luminescent center of the light-emitting layer a2. In contrast, asshown in FIG. 7B, when the thicknesses of the green light-emitting layera1 and the red light-emitting layer a2 are relatively as large as 20 nm,the luminescent centers of these light-emitting layers a1 and a2 areregarded as shifted from each other. As a result, as shown in FIG. 8,slopes in opposite directions appear in the spectral transmittancecurves of the interference filters corresponding to the greenlight-emitting layer a1 and the red light-emitting layer a2. Therefore,as the viewing angle increases, the transmittance of green lightdecreases whereas the transmittance of red light increases. Thus, acolor shift Occurs.

In the organic EL device according to the third embodiment, as shown inFIG. 9, a conductive transparent layer 18 having a refractive indexdifferent from the transparent layer 14 is formed on the transparentlayer 14, and the second electrode 12 is formed on the transparent layer18. Moreover, a fourth reflective interface 19 is formed between thetransparent layer 18 and the second electrode 12. In this case, thethird reflective interface 17 is formed between the transparent layer 14and the transparent layer 18. The fourth reflective interface 19 is setat a position such that light having the central wavelength λ1 of theemission spectrum of the first light-emitting layer 13 a is in theconstructive condition. By doing so, the interference filterscorresponding to the green light-emitting layer a1 and the redlight-emitting layer a2 have the spectral transmittance curves as shownin FIG. 10. Thus, it can be understood that an interference filterhaving a flat peak can be formed for light of the colors green and red.

When the stacking order of the green light-emitting layer a1 and the redlight-emitting layer a2 is reversed, the same advantage as above can beobtained by forming the fourth reflective interface 19 at a positionsuch that light having the central wavelength λ1 of the emissionspectrum of the first light-emitting layer 13 a is in the destructivecondition.

The luminance and chromaticity-viewing angle characteristics of theorganic EL device according to the third embodiment having the fourthreflective interface 19 are shown in FIGS. 11 and 12. It can beunderstood from FIGS. 11 and 12 that according to this organic ELdevice, the luminance and chromaticity-viewing angle characteristics areimproved further as compared with the organic EL device according to thefirst embodiment.

Example 1

Example 1 is an example corresponding to the first embodiment.

FIG. 13 shows an organic EL device according to Example 1. This organicEL device is a top emission-type organic EL device. As shown in FIG. 13,in this organic EL device, a first electrode 11, an organic layer 13, atransparent layer 14, and a second electrode 12 are sequentially stackedon a substrate 20 in that order from the lower side, and a passivationfilm 21 is formed on the second electrode 12.

The substrate 20 is formed, for example, of a transparent glasssubstrate or a semiconductor substrate (for example, a siliconsubstrate) and may be flexible. The first electrode 11 is an anodeelectrode also serving as a reflective layer and is formed from a lightreflective material, for example, aluminum (Al), aluminum alloy,platinum (Pt), gold (Au), chromium (Cr), and tungsten (W). The thicknessof the first electrode 11 is preferably set to be in the range of 100 to300 nm. The first electrode 11 maybe a transparent electrode. In thiscase, it is preferable to form a reflective layer made from a lightreflective material, for example, Pt, Au, Cr, and W, for the purpose offorming the first reflective interface 15 opposing the substrate 20.

The organic layer 13 has a structure in which a hole injection layer 13c, a hole transport layer 13 d, a first light-emitting layer 13 a, anelectron transport layer 13 e, an electron injection layer 13 f, aconnection layer 13 g, a hole transport layer 13 h, a secondlight-emitting layer 13 b, an electron transport layer 13 i, and anelectron injection layer 13 j are sequentially stacked in that orderfrom the lower side. The hole injection layer 13 c is formed, forexample, from hexaazatriphenylene (HAT) or the like. The hole transportlayer 13 d is formed, for example, from α-NPD[N,N′-di(1-naphthyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-di amine]. Thegreen light-emitting layer a1 of the first light-emitting layer 13 a isformed, for example, from Alq3 (tris-quinolinolaluminum complex), andthe red light-emitting layer a2 is formed, for example, from a materialobtained by doping pyrromethene-boron complex into rubrene used as ahost material. The electron transport layer 13 e is formed, for example,from BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline). The electroninjection layer 13 f is formed, for example, from lithium fluoride(LiF). The connection layer 13 g is formed, for example, from Alq3(8-hydroxyquinoline aluminum) doped with Mg (50) and hexaazatriphenylene(HAT). The hole transport layer 13 h also serving as the hole injectionlayer is formed, for example, from u-NPD. The second light-emittinglayer 13 b is formed from a light emitting material having the blue (B)emission color. Specifically, ADN (9,10-di(2-naphthyl)anthracene) isdeposited as a host material to form a film having a thickness of 20 nm.At that time, a diaminochrysene derivative is doped into the ADN as animpurity material by an amount of 5% in the relative thickness ratio,whereby the film can be used as a blue light-emitting layer. Theelectron transport layer 13 i is formed, for example, of BCP. Theelectron injection layer 13 j is formed, for example, of LiF.

The thickness of each layer of the organic layer 13 is preferably set inthe ranges of 1 to 20 nm for the hole injection layer 13 c, 15 to 100 nmfor the hole transport layer 13 d, 5 to 50 nm for the first and secondlight-emitting layers 13 a and 13 b, and 15 to 200 nm for the electroninjection layers 13 f and 13 j and the electron transport layers 13 eand 13 i. The thicknesses of the organic layer 13 and each constituentlayer are set to a value such that the optical film thicknesses thereofenable the above-mentioned operations.

The second reflective interface 16 is formed by forming a conductivetransparent layer 14 on the organic layer 13 and using the difference inthe refractive indices between the organic layer 13 and the transparentlayer 14. Moreover, the third reflective interface 17 is formed by usingthe difference in the refractive indices between the transparent layer14 and the second electrode 12. The transparent layer 14 may not be alayer made up of one layer but may be a stacked structure of two or moretransparent layers having different refractive indices depending on anecessary flat wavelength range and the viewing angle characteristics.

The second electrode 12 from which light is extracted is formed from ITOthat is generally used as a transparent electrode material, an oxide ofindium and zinc, and the like and is used as a cathode electrode. Thethickness of the second electrode 12 is in the range of 30 to 3000 nm,for example.

The second electrode 12 may also serve as the transparent layer 14, andin this case, the second reflective interface 16 is formed between theorganic layer 13 and the second electrode 12.

The passivation film 21 is formed from a transparent dielectricmaterial. The transparent dielectric may not necessarily have the samerefractive index as the material of the second electrode 12. When thesecond electrode 12 also serves as the transparent layer 14 as describedabove, the interface between the second electrode 12 and the passivationfilm 21 may serve as the second or third reflective interface 16 or 17by using the difference in the refractive indices thereof. As thetransparent dielectric material, silicon dioxide (SiO₂), silicon nitride(SiN), and the like can be used, for example. The thickness of thepassivation film 21 is in the range of 500 to 10000 nm, for example.

A semitransparent reflective layer may be formed between the organiclayer 13 and the transparent layer 14, as necessary. The semitransparentreflective layer is formed of a metal layer, for example, of magnesium(Mg), silver (Ag), or an alloy thereof, and the thickness is set to 5 nmor less, and preferably in the range of 3 to 4 nm or less.

Example 2

Example 2 is an example corresponding to the first embodiment.

FIG. 14 shows an organic EL device according to Example 2. This organicEL device is a bottom emission-type organic EL device. As shown in FIG.14, in this organic EL device, a passivation film 21, a second electrode12, an organic layer 13, and a first electrode 11 are sequentiallystacked on a transparent substrate 20 in that order from the lower side.In this case, light emitted from the side of the second electrode 12passes through the substrate 20 to be extracted to the outside. Thesecond electrode 12 also serves as the transparent layer 14 ofExample 1. Moreover, a second reflective interface 16 is formed betweenthe organic layer 13 and the second electrode 12, and a third reflectiveinterface 17 is formed between the second electrode 12 and thepassivation film 21. Other configurations are the same as Example 1.

4. Fourth Embodiment Organic EL Illumination Apparatus

FIG. 15 shows an organic EL illumination apparatus according to a fourthembodiment.

As shown in FIG. 15, in this organic EL illumination apparatus, anorganic EL device 31 according to any one of the first to thirdembodiments is mounted on a transparent substrate 30. In this case, theorganic EL device 31 is mounted on the substrate 30 with the side of thesecond electrode 12 facing downward. Thus, light emitted from the sideof the second electrode 12 passes through the substrate 30 to beextracted to the outside. A sealing substrate 32 is provided so as toface the substrate 30 with the organic EL device 31 interposedtherebetween, and the outer peripheral portions of the sealing substrate32 and the substrate 30 are sealed by a sealing material 33. Thetop-view shape of the organic EL illumination apparatus is chosen asnecessary, and is square or rectangular, for example. Although only oneorganic EL device 31 is shown in FIG. 15, a plurality of organic ELdevices 31 may be mounted on the substrate 30 in a desired layout, asnecessary. The details of a configuration of the organic EL illuminationapparatus other than the organic EL device 31 and the otherconfigurations are the same as those of a known organic EL illuminationapparatus.

According to the fourth embodiment, since the organic EL device 31according to any one of the first to third embodiments is used, it ispossible to realize an organic EL illumination apparatus which serves asa field light source having good intensity distribution properties andsmall viewing-angle dependency (that is, a variation in intensity orcolor in accordance with an illumination direction is very small).Moreover, by choosing the emission color of the organic EL device 31 bydesigning the first and second light-emitting layers 13 a and 13 b, itis possible to obtain various emission colors other than white emissioncolor. Thus, it is possible to realize an organic EL illuminationapparatus having excellent color rendering properties.

5. Fifth Embodiment Organic EL Display Apparatus

FIG. 16 shows an organic EL display apparatus according to a fifthembodiment. This organic EL display apparatus is an active matrix-typedisplay apparatus.

As shown in FIG. 16, in this organic EL display apparatus, a drivingsubstrate 40 and a sealing substrate 41 are provided so as to face eachother, and the outer peripheral portions of the driving substrate 40 andthe sealing substrate 41 are sealed by a sealing material 42. In thedriving substrate 40, pixels formed of the organic EL device 43according to any one of the first to third embodiments are formed on atransparent glass substrate, for example, in a 2-dimensional array form.On the driving substrate 40, a thin-film transistor used as a pixeldriving active device is formed for each pixel. In addition, on thedriving substrate 40, scanning lines, current supply lines, and datalines for driving the thin-film transistors of the respective pixels areformed in the vertical and horizontal directions. A display signalcorresponding to every display pixel is supplied to the thin-filmtransistors of the respective pixels, and the pixels are driven inaccordance with the display signals, and images are displayed. Thedetails of a configuration of the organic EL display apparatus otherthan the organic EL device 43 and the other configurations are the sameas those of a known organic EL display apparatus.

This organic EL display apparatus can be used as a color displayapparatus as well as a black-and-white display apparatus. When thisorganic EL display apparatus is used as a color display apparatus, anRGB color filter is provided on the side of the driving substrate 40,specifically between the second electrode 12 of the organic EL device 43and the driving substrate 40, for example.

According to the fifth embodiment, since the organic EL device 31according to any one of first to third embodiments is used, it ispossible to realize an organic EL display apparatus which has a highdisplay quality and in which a variation in luminance and hue inaccordance with a viewing angle is very small.

While specific embodiments and examples of the present invention havebeen described in detail, the present invention is not limited to thoseembodiments and examples described above, but various changes andmodifications may be effected therein based on the technical spirit ofthe invention.

For example, numerical values, structures, configurations, shapes,materials, and the like shown in the foregoing embodiments and examplesare no more than mere examples, and other appropriate numerical values,structures, configurations, shapes, materials, and the like, can beoptionally used.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2010-018492 filedin the Japan Patent Office on Jan. 29, 2010, the entire contents ofwhich is hereby incorporated by reference.

1. A light-emitting device comprising: an organic layer which isinterposed between a first electrode and a second electrode and in whicha first light-emitting layer and a second light-emitting layer emittinglight of single colors or two or more different colors in a visiblewavelength region are sequentially included at mutually separatedpositions in that order in a direction from the first electrode to thesecond electrode; a first reflective interface which is provided on theside of the first electrode so as to reflect light emitted from thefirst light-emitting layer and the second light-emitting layer to beemitted from the side of the second electrode; and a second reflectiveinterface and a third reflective interface which are sequentiallyprovided on the side of the second electrode at mutually separatedpositions in that order in a direction from the first electrode to thesecond electrode, wherein when an optical distance between the firstreflective interface and a luminescent center of the firstlight-emitting layer is L11, an optical distance between the firstreflective interface and a luminescent center of the secondlight-emitting layer is L21, an optical distance between the luminescentcenter of the first light-emitting layer and the second reflectiveinterface is L12, an optical distance between the luminescent center ofthe second light-emitting layer and the second reflective interface isL22, an optical distance between the luminescent center of the firstlight-emitting layer and the third reflective interface is L13 , anoptical distance between the luminescent center of the secondlight-emitting layer and the third reflective interface is L23, acentral wavelength of an emission spectrum of the first light-emittinglayer is Xl, and a central wavelength of an emission spectrum of thesecond light-emitting layer is λ2, L11, L21, L12, L22, L13, and L23 arechosen so as to satisfy a11 the expressions (1) to (6) and at least oneof the expressions (7) and (8).2L11/λ11+φ1/2π=0  (1)2L21/λ21+φ1/2π=n (where n≧1)  (2)λ1−150<λ11<λ1+80  (3)λ2−30<λ21<λ2+80  (4)2L12/λ12+φ2/2π=m′+1/2 and 2L13/λ13+φ3/2π=m=m″, or 2L12/λ12+φ2/2π=m′ and2L13/λ13+φ3/2π=m″+1/2  (5)2L22/λ22+φ2/2π=n′+1/2 and 2L23/λ23+φ3/2π=n″, or 2L22/λ22+φ2/2π=n′ and2L23/λ23+φ3/2π=n″+1/2, or 2L22/λ22+φ2/2π=n′+1/2 and2L23/λ23+φ3/2π=n″+1/2  (6)λ22<λ2−15 or λ23>λ2+15  (7)λ23<λ2−15 or λ22>λ2+15  (8) where m′, m″, n, n′, n″ are integers, λ1,λ2, λ11, λ21, λ12, λ22, λ13, and λ23 are in units of nm, φ1 is a phaseshift occurring when light of each wavelength is reflected by the firstreflective interface, φ2 is a phase shift occurring when light of eachwavelength is reflected by the second reflective interface, and φ3 is aphase shift occurring when light of each wavelength is reflected by thethird reflective interface.
 2. The light-emitting device according toclaim 1, wherein peaks of a spectral transmittance curve of aninterference filter of the light-emitting device are substantially flat,or the slopes thereof are substantially the same in the wavelength rangeof all emission colors.
 3. The light-emitting device according to claim2, wherein a decrease of luminance at a viewing angle of 45° is 300 orless with respect to luminance at a viewing angle of 0°, and achromaticity shift of Δuv≦0.015 is obtained.
 4. The light-emittingdevice according to claim 3, wherein n=1.
 5. The light-emitting deviceaccording to claim 1, wherein the first electrode, the organic layer,and the second electrode are sequentially stacked on a substrate.
 6. Thelight-emitting device according to claim 5, wherein a transparentelectrode layer having a thickness of 1 μm or more, a transparentinsulating layer, a resin layer, a glass layer, or an air layer isformed on an outer side of the third reflective interface.
 7. Thelight-emitting device according to claim 1, wherein the secondelectrode, the organic layer, and the first electrode are sequentiallystacked on a substrate.
 8. The light-emitting device according to claim7, wherein a transparent electrode layer having a thickness of 1 μm ormore, a transparent insulating layer, a resin layer, a glass layer, oran air layer is formed on an outer side of the third reflectiveinterface.
 9. The light-emitting device according to claim 1, wherein ametal layer having a thickness of 5 nm or less is formed between thesecond light-emitting layer and the second electrode.
 10. Thelight-emitting device according to claim 1, wherein at least one of thefirst reflective interface, the second reflective interface, and thethird reflective interface is divided into a plurality of reflectiveinterfaces .
 11. The light-emitting device according to claim 1, whereinwhen the luminescent centers of light-emitting layers of the first orsecond light-emitting layer emitting light of two or more differentcolors may not be regarded as identical, the light-emitting devicefurther includes a reflective layer which is provided so as to maintainthe flatness of the peaks of a spectral transmittance curve of aninterference filter of the light-emitting device.
 12. An illuminationapparatus comprising: at least one light-emitting device, wherein thelight-emitting device includes an organic layer which is interposedbetween a first electrode and a second electrode and in which a firstlight-emitting layer and a second light-emitting layer emitting light ofsingle colors or two or more different colors in a visible wavelengthregion are sequentially included at mutually separated positions in thatorder in a direction from the first electrode to the second electrode; afirst reflective interface which is provided on the side of the firstelectrode so as to reflect light emitted from the first light-emittinglayer and the second light-emitting layer to be emitted from the side ofthe second electrode; and a second reflective interface and a thirdreflective interface which are sequentially provided on the side of thesecond electrode at mutually separated positions in that order in adirection from the first electrode to the second electrode, wherein whenan optical distance between the first reflective interface and aluminescent center of the first light-emitting layer is L11, an opticaldistance between the first reflective interface and a luminescent centerof the second light-emitting layer is L21, an optical distance betweenthe luminescent center of the first light-emitting layer and the secondreflective interface is L12, an optical distance between the luminescentcenter of the second light-emitting layer and the second reflectiveinterface is L22, an optical distance between the luminescent center ofthe first light-emitting layer and the third reflective interface isL13, an optical distance between the luminescent center of the secondlight-emitting layer and the third reflective interface is L23, acentral wavelength of an emission spectrum of the first light-emittinglayer is λ1, and a central wavelength of an emission spectrum of thesecond light-emitting layer is λ2, L11, L21, L12, L22, L13, and L23 arechosen so as to satisfy all the expressions (1) to (6) and at least oneof the expressions (7) and (8).2L11/λ11+φ1/2π=0  (1)2L21/λ21+φ1/2π=n (where n≧1)  (2)λ1−150<λ11<λ1+80  (3)λ2−30<λ21<λ2+80  (4)2L12/λ12+φ2/2π=m′+1/2 and 2L13/λ13+φ3/2π=m″, or 2L12/λ12+φ2/2π=m′ and2L13/λ13+φ3/2π=m″+1/2  (5)2L22/λ22+φ2/2π=n′+1/2 and 2L23/λ23+φ3/2π=n″, or 2L22/λ22+φ2/2π=n′ and2L23/λ23+φ3/2π=n″+1/2, or 2L22/λ22+φ2/2π=n′+1/2 and2L23/λ23+φ3/2π=n″+1/2  (6)λ22<λ2−15 or λ23>λ2+15  (7)λ23<λ2−15 or λ22>λ2+15  (8) where m′, m″, n, n′, n″ are integers, λ1,λ2, λ11, λ21, λ12, λ22, λ13, and λ23 are in units of nm, φ1 is a phaseshift occurring when light of each wavelength is reflected by the firstreflective interface, φ2 is a phase shift occurring when light of eachwavelength is reflected by the second reflective interface, and φ3 is aphase shift occurring when light of each wavelength is reflected by thethird reflective interface.
 13. A display apparatus comprising: at leastone light-emitting device, wherein the light-emitting device includes anorganic layer which is interposed between a first electrode and a secondelectrode and in which a first light-emitting layer and a secondlight-emitting layer emitting light of single colors or two or moredifferent colors in a visible wavelength region are sequentiallyincluded at mutually separated positions in that order in a directionfrom the first electrode to the second electrode; a first reflectiveinterface which is provided on the side of the first electrode so as toreflect light emitted from the first light-emitting layer and the secondlight-emitting layer to be emitted from the side of the secondelectrode; and a second reflective interface and a third reflectiveinterface which are sequentially provided on the side of the secondelectrode at mutually separated positions in that order in a directionfrom the first electrode to the second electrode, wherein when anoptical distance between the first reflective interface and aluminescent center of the first light-emitting layer is L11, an opticaldistance between the first reflective interface and a luminescent centerof the second light-emitting layer is L21, an optical distance betweenthe luminescent center of the first light-emitting layer and the secondreflective interface is L12, an optical distance between the luminescentcenter of the second light-emitting layer and the second reflectiveinterface is L22, an optical distance between the luminescent center ofthe first light-emitting layer and the third reflective interface isL13, an optical distance between the luminescent center of the secondlight-emitting layer and the third reflective interface is L23, acentral wavelength of an emission spectrum of the first light-emittinglayer is λ1, and a central wavelength of an emission spectrum of thesecond light-emitting layer is λ2, L11, L21, L12, L22, L13, and L23 arechosen so as to satisfy all the expressions (1) to (6) and at least oneof the expressions (7) and (8).2L11/λ11+φ1/2π=0  (1)2L21/λ21+φ1/2π=n (where n≦1)  (2)λ1−150<λ11<λ1+80  (3)λ2+30<λ21<λ2+80  (4)2L12/λ12+φ2/2π=m′+1/2 and 2L13/λ13+φ3/2π=m″, or 2L12/λ12+φ2/2π=m′ and2L13/λ13+φ3/2π=m″+1/2  (5)2L22/λ22+φ2/2π=n′+1/2 and 2L23/λ23+φ3/2π=n″, or 2L22/λ22+φ2/2π=n′ and2L23/λ23+φ3/2π=n″+1/2, or 2L22/λ22+φ2/2π=n′+1/2 and2L23/λ23+φ3/2π=n″+1/2  (6)λ22<λ2−15 or λ23>λ2+15  (7)λ23<λ2−15 or λ22>λ2+15  (8) where m′, m″, n, n′, n″ are integers, λ1,λ2, λ11, λ21, λ12, λ22, λ13, and λ23 are in units of nm, φ1 is a phaseshift occurring when light of each wavelength is reflected by the firstreflective interface, φ2 is a phase shift occurring when light of eachwavelength is reflected by the second reflective interface, and φ3 is aphase shift occurring when light of each wavelength is reflected by thethird reflective interface.
 14. The display apparatus according to claim13, further comprising: a driving substrate on which an active device isprovided so as to supply a display signal corresponding to every displaypixel to the light-emitting device; and a sealing substrate provided soas to face the driving substrate, wherein the light-emitting device isdisposed between the driving substrate and the sealing substrate. 15.The display apparatus according to claim 14, wherein a color filterwhich transmits light emitted from the side of the second electrode isprovided on a substrate that is disposed on the side of the secondelectrode of the light-emitting device among the driving substrate andthe sealing substrate.